# std::atomic_ref<T>::operator&=,|=,^=

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< cpp‎ | atomic‎ | atomic ref

Provided only when `T` is an integral type other than cv bool |  |
value_type operator&=( value_type arg ) const noexcept; | (1) | (since C++20)
value_type operator|=( value_type arg ) const noexcept; | (2) | (since C++20)
value_type operator^=( value_type arg ) const noexcept; | (3) | (since C++20)

Atomically replaces the current value of the referenced object with the result of computation involving the previous value and arg. These operations are read-modify-write operations.

- operator&= performs atomic bitwise AND. Equivalent to return fetch_and(arg) & arg;.
- operator!= performs atomic bitwise OR. Equivalent to return fetch_or(arg) | arg;.
- operator^= performs atomic bitwise XOR. Equivalent to return fetch_xor(arg) ^ arg;.

These overloads participate in overload resolution only if std::is_const_v<T> is false.

### Parameters

arg | - | the argument for the arithmetic operation

### Return value

The resulting value (that is, the result of applying the corresponding binary operator to the value immediately preceding the effects of the corresponding member function).

### Notes

Unlike most compound assignment operators, the compound assignment operators for `atomic_ref` do not return a reference to their left-hand arguments. They return a copy of the stored value instead.

### Example

| This section is incomplete Reason: no example

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 3508 (P3323R1) | C++20 | compound assignment operators were meaningless for const T | constrained to accept only non-const `T`

### See also

fetch_and | atomically performs bitwise AND between the argument and the value of the referenced object and obtains the value held previously (public member function)
fetch_or | atomically performs bitwise OR between the argument and the value of the referenced object and obtains the value held previously (public member function)
fetch_xor | atomically performs bitwise XOR between the argument and the value of the referenced object and obtains the value held previously (public member function)
operator++operator++(int)operator--operator--(int) | atomically increments or decrements the referenced object by one (public member function)
operator+=operator-= | atomically adds to or subtracts from the referenced value (public member function)

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